title: Physiologically dependent appearance of a low density region that corresponds to the tunnel through the 50S part of the 70S ribosome.
abstract: Ribosomes have different conformations in cells that are starved for a required amino acid (giving aminoacyl.tRNA starvation), or treated with kirromycin (blocking EF-Tu.GDP release), or are in exponential growth. A tunnel spans the 50S ribosome from a location facing the 70S ribosomal intersubunit space to the back side of the subunit in Escherichia coli cells. Here we have analyzed the internal low density region that corresponds to this tunnel in ribosomes in vivo. The data suggest that the tunnel is opened in connection with spatial separation of the subunits in ribosomes that have an empty A-site due to starvation for aminoacyl.tRNA. A region that corresponds to this tunnel can be found in the more compact structure of ribosomes in kirromycin-treated cells only after a substantial removal of low density material. This region is even less prominent in ribosomes in undefined working modes in growing bacteria. The data suggest that appearance of the tunnel through the 50S ribosomal subunit is working-mode dependent and it is not a characteristic feature of the major fraction of the ribosomal population in growing cells.
authors.affiliation: Department of Microbiology, Stockholm University, Stockholm, S-106 91, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: L G
authors.initials: LG
authors.lastname: Ofverstedt
authors.forename: L
authors.initials: L
authors.lastname: Pettersson-Landén
authors.forename: U
authors.initials: U
authors.lastname: Skoglund
authors.forename: L A
authors.initials: LA
authors.lastname: Isaksson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008854:Microscopy, Electron / Q000379:methods; D011728:Pyridones / Q000494:pharmacology; D012270:Ribosomes / Q000648:ultrastructure*; D014364:Tryptophan / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D011728:Pyridones; D014364:Tryptophan; C008536:mocimycin